Process of producing protective and resistant coatings



Patented Nov. 9, 1926.

UNITED STATES a 1,606,159 PATENT orr ca.

COLIN 3. mm: AND LI c111 PAN, or NEW YORK, N. Y, ASSIGNORS T CHEMICAL TREAT- MEN! COMPANY, INC., OF NEW YORK N. Y., A CORPQRATION OF NEW YORK A PROCESS OF PRODUGING IROTECT IVE AND RESISTANT COATINGS.-

lqo Drawing. Application filed December lent qualities, by an economical and readily performed procedure.

The present invention accordingly provides an improved process of producing coatings having excellent protective and resistant properties (that is, resistance to corrosion, acids, wear) which process is carried out in readily performed operations, resulting in an economical production of the coatings. The process further enables one to obtain bright coatings notwithstanding the use of heat at elevated temperatures, and the susceptibility of the plated metal to oxidation and discoloration at the elevated temperature, when exposed to air.

According to the present invention. a foundation metal as for example iron, steel, etc.,

is coated with chromium, preferably by electrodeposition. This coating may be from mill to 1 mill thick, and may be produced according to the method of plating set forth in the application of Fink and Eldridge filed August 26, 1924, Serial No. 734,193, and

other applications of Fink and associates. After plating, the metal article having thereon the plate is, without the necessity for 40 preparator treatment, immersed in a bath of molten ead. This bath of lead is preferably maintained at a temperature somewhat above its melting point, a temperature of 800 C. bein employed -in practice.

The artic e is allowed to remain in the bath of lead until it reaches the tem erature of the bath, and preferably somew at longer. The time will va with the size and shape of the articles. ith small articles having about 24 square inches surface, and weighing about 4 ounces, the time of immersionis'from one to two hours,

The heating of the article has the effect of eliminating pin-hole defects in the chromium plate, producing a healing of these is, 1925. Serial No. 76,312.,

defects, and probably produces a limited al-- loying of the chromium plate with the underlyin foundation metal.

A ter the plated article has been sufficientl heat treated in the bath, it is remove therefrom.

After ,removal, the treated article has a film of lead adhering to the chromium plate.

The surface of the chromium,chowever, Is

not discolored, and appears as a bright surface after removal of the lead film. This film of lead. where a bright non-tarnishing surface 1s desired, is then preferably re-' moved, and this removal may be effected in a variety of ways. -It may be conveniently effected by abrasion, inasmuch as chromium is very much harder than lead, and abrasives may be used which will readily attack the lead. but will notlaflect the chromium. For example, a so-called scratch-brush ma be used over 'thesurface to removethe l ead Moreover, the lead may be removed by acids, an acid being selected which is inactive toward chromium and active toward lead, as for example nitric acid.

The remoial of lead by acid is preferably also employed-after a treatment of the lead v The invention may be carried out'b'y other modes of procedure than that herein specifically described.

What is claimed is:-

1. A method of producing protective and resistant coatings of metals which are dis colored and oxidized when heated 'in air, comprising plating a foundation-metal with the protective metal, and immersing the plated metal article in a molten bath of lead to eliminate pin-holedefects in said plate by heat-treatment, without "producing discoloration of said protective metal.

2. A method of producing protective and resistant coatings of metals whiehare discolored and oxidized when heated in air, comprising plating a foundation-metal with the protective metal, and immersing the plated metal article in a molten bath of lead to eliminate pin-hole defects in said plate by heat-treatment, without producing discoloration of said portective metal, and removing the film of lead remaining on the.

plate after removal from the bath.

3. A method of producing protective and resistant coatingsof metals which are'discolored and oxidized when heated in air,

comprising plating a foundation-metal with the protective metal, and immersing the plated metal article in a molten bath of lead to eliminate pin-hole defects in said plate by heat-treatment, without producing discoloration of 'said protective metal, and rem'ovingby abrasion the film of lead remain ing on the plate after removal from the bath.

4; A methodof producing protective and resistant coatin s of metals which are discolored and oxidized when heated in air, comprising plating a foundation-metal with the protective metal, and immersing the plated metal article in a molten bath of lead to eliminate pin-hole defects in said plate by heat-treatment, without producing discoloration of said protective metal, and

removing by acid the film of lead remaining on the plate after removal from the bath.

5. A method of producing protective and;

resistant coatingsof metals which are, discolored and oxldized when heated in air, comprising plating a foundation-metal with the protective metal, and immersing the I plated metal article in a molten bath of lead to eliminate pin-hole defects in said plate by heat-treatment, without producing dis coloration of said protective metal, and re- I moving by abrasion and acid the film of lead remaining on the plate after removal'f -rom v the bath 6. A method of producing protective and resistant bright coatings of chromium, eom-,

chromium, immersing the chromium-plated article in a molten bath'of lead to eliminatepin-hole defects in said plate by heattreatment, without producin a discoloration of said chromium plate, an removing the film of 'lead rem aining on the plate after.

removal from the bath.

In witness whereof, we have hereunto signed our names.

COLIN G. FINK.

LI C, PAN. 

